快活林资源网 Design By www.csstdc.com
实例解析:
select to_char(log.date, 'yyyy-MM-dd HH24') as hour, log.exten, sum(case log.grade when '1' then 1 else 0 end) as "1", sum(case log.grade when '2' then 1 else 0 end) as "2", sum(case log.grade when '3' then 1 else 0 end) as "3", sum(case log.grade when '4' then 1 else 0 end) as "4", sum(case log.grade when '5' then 1 else 0 end) as "5", log.direction from iface_satisfaction_investigation as log where log.date >= '2017-08-03 00:00:00' and log.date < '2017-08-04 00:00:00' group by hour,log.exten,log.direction order by hour,log.exten,log.direction asc
to_char:用于查询时间格式化,to_char(log.date, 'yyyy-MM-dd HH24'),大致的结果是:2017-08-03 13
sum():毫无疑问是用来计算总和的。
sum(case log.grade when '1' then 1 else 0 end)
是计算什么呢?
他的意思就是:
计算grade这个列的值为1的时候有多少行,后面的sum(……)就类推了。
其他的也没有什么好讲的了
补充:PostgreSQL常用的统计信息
我就废话不多说了,大家还是直接看代码吧~
/*计算表的空间大小*/ select oid,table_schema as "模式", table_name as "表名", row_estimate::bigint as "表中的行数(估计值)", pg_size_pretty(total_bytes) as "总大小", pg_size_pretty(table_bytes) as "表大小", pg_size_pretty(index_bytes) as "索引大小", pg_size_pretty(toast_bytes) as "toast表总大小" from ( select *, total_bytes-index_bytes-coalesce(toast_bytes,0) as table_bytes from ( select c.oid, nspname as table_schema, relname as table_name, c.reltuples as row_estimate, pg_total_relation_size(c.oid) as total_bytes, pg_indexes_size(c.oid) as index_bytes, pg_total_relation_size(reltoastrelid) as toast_bytes from pg_class c left join pg_namespace n on n.oid = c.relnamespace where relkind = 'r' ) t1 ) t2 order by 2,3; /*统计用户表信息*/ select schemaname as "模式", relname as "表名", seq_scan as "顺序扫描的次数", seq_tup_read as "顺序扫描获取活动行的数量", idx_scan as "索引扫描次数", idx_tup_fetch as "索引扫描获取活动行的数量", n_tup_ins as "累计插入的行数", n_tup_upd as "累计更新的行数(包含HOT 更新的行)", n_tup_del as "累计删除的行数", n_live_tup as "当前活动行估计数量", n_dead_tup as "当前死亡行的估计数量", n_mod_since_analyze as "最后一次分析后被修改的行估计数量", last_vacuum as "上次被手动清理的时间(不统计VACUUM FULL)", last_autovacuum as "上次自动清理的时间", last_analyze as "上次手动分析的时间", last_autoanalyze as "上次自动清理分析的时间", vacuum_count as "手动清理的次数", autovacuum_count as "自动清理的次数", analyze_count as "手动分析的次数", autoanalyze_count as "自动分析的次数", pg_size_pretty(pg_table_size(relid)) as "表大小(不包含索引)" from pg_stat_user_tables order by 1; /*统计用户表IO信息*/ select schemaname as "模式", relname as "表名", heap_blks_read as "读取的磁盘块数量", heap_blks_hit as "缓冲区命中数量", idx_blks_read as "表上所有索引读取的磁盘块数", idx_blks_hit as "表上的所有索引缓冲区命中数量", toast_blks_read as "TOAST表(如果有)读取的磁盘块数", toast_blks_hit as "TOAST表(如果有)缓冲区命中数量", tidx_blks_read as "TOAST表索引(如果有)读取的磁盘块数", tidx_blks_hit as "TOAST表索引(如果有)缓冲区命中数量" from pg_statio_user_tables order by 1; /*统计用户索引信息*/ select indexrelid, schemaname as "模式", relname as "索引所在的表名称", indexrelname as "索引名称", idx_scan as "索引扫描次数", idx_tup_read as "索引扫描返回的索引项数量", idx_tup_fetch as "简单索引扫描获取的活动行数量", pg_size_pretty(pg_relation_size(indexrelid)) as "索引大小" from pg_stat_user_indexes order by 1,2; /*追踪函数,需要打开track_functions参数(默认关闭)*/ select * from pg_stat_user_functions;
以上为个人经验,希望能给大家一个参考,也希望大家多多支持。如有错误或未考虑完全的地方,望不吝赐教。
快活林资源网 Design By www.csstdc.com
广告合作:本站广告合作请联系QQ:858582 申请时备注:广告合作(否则不回)
免责声明:本站资源来自互联网收集,仅供用于学习和交流,请遵循相关法律法规,本站一切资源不代表本站立场,如有侵权、后门、不妥请联系本站删除!
免责声明:本站资源来自互联网收集,仅供用于学习和交流,请遵循相关法律法规,本站一切资源不代表本站立场,如有侵权、后门、不妥请联系本站删除!
快活林资源网 Design By www.csstdc.com
暂无评论...
RTX 5090要首发 性能要翻倍!三星展示GDDR7显存
三星在GTC上展示了专为下一代游戏GPU设计的GDDR7内存。
首次推出的GDDR7内存模块密度为16GB,每个模块容量为2GB。其速度预设为32 Gbps(PAM3),但也可以降至28 Gbps,以提高产量和初始阶段的整体性能和成本效益。
据三星表示,GDDR7内存的能效将提高20%,同时工作电压仅为1.1V,低于标准的1.2V。通过采用更新的封装材料和优化的电路设计,使得在高速运行时的发热量降低,GDDR7的热阻比GDDR6降低了70%。
更新日志
2024年12月28日
2024年12月28日
- 小骆驼-《草原狼2(蓝光CD)》[原抓WAV+CUE]
- 群星《欢迎来到我身边 电影原声专辑》[320K/MP3][105.02MB]
- 群星《欢迎来到我身边 电影原声专辑》[FLAC/分轨][480.9MB]
- 雷婷《梦里蓝天HQⅡ》 2023头版限量编号低速原抓[WAV+CUE][463M]
- 群星《2024好听新歌42》AI调整音效【WAV分轨】
- 王思雨-《思念陪着鸿雁飞》WAV
- 王思雨《喜马拉雅HQ》头版限量编号[WAV+CUE]
- 李健《无时无刻》[WAV+CUE][590M]
- 陈奕迅《酝酿》[WAV分轨][502M]
- 卓依婷《化蝶》2CD[WAV+CUE][1.1G]
- 群星《吉他王(黑胶CD)》[WAV+CUE]
- 齐秦《穿乐(穿越)》[WAV+CUE]
- 发烧珍品《数位CD音响测试-动向效果(九)》【WAV+CUE】
- 邝美云《邝美云精装歌集》[DSF][1.6G]
- 吕方《爱一回伤一回》[WAV+CUE][454M]